[CONTRIBUTION FROM THE DANIEL SIEFFRESEARCH INSTITUTE, REHOVOTH, PaLESTINE ]
SYNTHESES AND REACTIONS OF SUBSTITUTED CY-NAPHTHOQUINONES ERNST BERGMANN
AND
FELIX BERGMANN
Received May $5, 1958
Fieser and co-workers have observed a very peculiar reaction of 2,6dimethyl-1 ,4-naphthoquinone' with diazomethane-reaction taking place in the free 3 position, coupling two quinone molecules by a methylene bridge. In order to study this reaction, which is somewhat similar to the known reactions of diazomethane with nitroso compounds and thioketones2, we investigated the synthetic possibilities leading to 2-phenyl6 ,7-dimethyl- and to 2 ,6 ,7-trimethyl-l,4-naphthoquinone and the behavior of these substances. Furthermore, the chemical reactions of 2 ,3-dimethylnaphthoquinone have been studied for comparative purposes. I. The obvious method was the diene synthesis, which, however, as far as we know, has been carried as far as the stage of the true naphthoquinones only for simple cases as described in a patent of I. G. Farbenindustrie A. G.3 Toluquinone, with 2 ,3-dimethylbutadiene, gives the normal addition product (I), m.p. 94', in boiling benzene or without solvent at 100-l10°4. A t 150-170°, two products have been isolated, one, m.p. 223-224', which is isomeric with (I), and - sometimes - a second one, m.p. 110'. The higher-melting substance, undoubtedly, is 2,6,7trimethy1-5,8-dihydro-lI 4-dihydroxynaphthalene (11), as it is produced by isomerisation of (I) with hydrobromic acid5. It is the first case to our knowledge, in which this type of isomerisation has been found to occur spontaneously in the course of synthesis. The lower-melting product (m.p. l l O o ) , on the other hand, is the desired 2,6,7-trimethyl-a-naphthoquinone (111). That follows apart from the analysis, from the following FIESER AND SELIGMANN, J . Am. Chem. Xoc., 66, 2690 (1934); FIESER AND HARTibid., 67, 1479 (1935). It may be noted that the reaction product, m.p. 293", assumed to be a diquinone is in fact a hydroquinone, as ferric chloride converts it into the real diquinone, m.p. 249". 2 See, e.g., STAUDINGER AND MIESCHER,Helv. Chim. Acta, 2, 534 (1919); BERGMANN, MAGAT, AND WAGENBERG, Ber., 63,2576 (1930). British Patent 324 661; cf. Chem. Zentr., 1930, 11, 809. 4 In accordance with the observation of CHUANG AND CHAN,Ber., 68, 876 (1935), toluquinone reacts with 1 mole of the diene only. 6 DIELSAND ALDER,ibid., 62, 2337 (1929). 125 1
WELL,
126
ERNST BERGMANN AND FELIX BERGMANN
observations: I1 is oxidised by ferric chloride to give 2,6,7-trimethyl5,8-dihydro-a-naphthoquinone(IV), m.p. 129", and this, on selenium dehydrogenation, is converted into the substance, m.p. 1lo", therefore 111. The same end-product is produced directly by selenium dehydrogenation of I. 0
0
OH
I
I1
IV
V
I11
VI
With phenylquinone too, which we used for the first time for diene synthesis6, 2 ,3-dimethylbutadiene reacts differently according to conditions. A t 100" without diluent the normal 2-phenyl-6,7-dimethyl5 ,8,9 ,10-tetrahydro-a-naphthoquinone (V), m.p. 113-114", is formed, while at elevated temperatures the desired 2-phenyl-6 ,7-dimethyl-a-naphthoquinone (VI, X=H) map. 127O, is formed, although in trivial yield*. Two ways are open for its preparation in larger quantities: V is converted by hydrobromic acid into the isomeric hydroquinone m.p. 137", then by ferric chloride into 2-phenyl-6 ,7-dimethyl-5 ,8-dihydro-a-naphthoquinone1 m.p. 119", which may be dehydrogenated by selenium. Or, the primary addition product, m.p. 113-114" (V), is directly subjected to selenium dehydrogenation, and the 2-phenyl-6 ,7-dimethyl-1 ,4-dihydroxynaphthalene (m.p. 197-198") obtained is oxidised subsequently by means of ferric chloride solution. Obviously, V, on heating, is first isomerized (see above) ; 6
On some experiments with 2,5-diphenylquinone, see ALLEN AND RUDORFF,
Can. J. Research 16B, 321 (1937); C. A . , 32, 124 (1938).
* Cyclopentadiene, also, with phenylquinone, gives the normal addition product, m.p. 79-80", in benzene solution.
SYNTHESES OF SUBSTITUTED a-NAPHTHOQUINONES
127
then selenium acts exclusively on the supernumerary nuclear hydrogen atoms. When we applied t o V or to 2-phenyl-6 7-dimethyl-l,4-dihydroxynaphthalene (m.p. 197-198") the oxidation by air in presence of alkali, which has given very favorable results in the anthraquinone seriess, we obtained 3-hydroxy-2-phenyl-6 7-dimethyl-a-naphthoquinone, m.p. 157158" (VI, X=OH) which exhibited all the characteristic features of those hydroxyquinones. Our observation parallels the formation of hydroxyjuglone from juglone', and the synthesis of phthiocole by Anderson and Newmans. 11. With diuzomethune I gives immediately a colourless addition product (VII), m.p. 142". This is decomposed in boiling ligroin (130°), yielding a nitrogen-free substance, for which we would suggest the formula (VIII) of 2 3 , 6 , 7-tetramethyld 8, 9 , 10-tetrahydro-a-naphthoquinone. The substance could not be isolated in the crystalline state, but gave a crystalline derivative (IX), m.p. 155-156*, on treatment with hydrobromic acid and subsequent dehydrogenation with ferric chloride solution. In the same way, 2 6 7-trimethyl-a-naphthoquinone (111) is converted by diazomethane into 2 3 6 7-tetramethyl-a-naphthoquinone,m.p. 167168", no "bimolecular" product being formed, as in the case of 2,6-dimethylnaphthoquinone, described by Fieser and co-workers. We have been able to isolate along with Fieser's substance, a low-melting by-product which according to its properties most probably is 2 , 3 6-trimethylnaphthoquinone. Furthermore, one of the products formed from 2-methylnaphthoquinone, on interaction with diazomethane, proved to be 2 3-dimethyl-a-naphthoquinone. It appears that diazomethane, even when the nuclear quinone double bond is partly blocked, adds primarily-at least to a certain extent-in the normal way, forming a pyrazoline detivative. Thermally, then, nitrogen is split off, and by rearrangement of the radical nuclear methylation takes place. The non-methylated a-naphthoquinone is the only case where no such methylation has been observed9. The occurrence of nuclear methylation supports satisfactorily formula VI1 with regard to the direction of the entering diazomethane molecule. Diazomethane, apparently, parallels completely the diene additions of those quinones. A further example in this direction is supplied by our observation, that ~ M Y L I U SB,e y . , 18, 469 (1885). * ANDERSON AND NEWMAN, J . Biol. Chem., 101, 773 (1933); 103, 197, 405 (1933). 9 PECHMANN AND SEEL,Ber., 32, 2297 (1899); FIESER AND PETERS, J . Am. Chem. SOC.,53, 4080 (1931).
128
EIZNST BERGMANN AND FELIX BERGMANN
0
0
VI1
Ix
VI11
X
%bromo-a-naphthoquinone adds diazomethane to give a condensation product which easily loses hydrogen bromide, yielding a-naptho[2,3]pyrazole-4,9-dione (X). The analogous observation with regard to diene syntheses, has recently been reported by Fieser and Dundo. The above-reported ,nuclear me6hylation is interesting both from a theoretical and from a preparative point of view. It is superficially reminiscent of the well-known conversion of aldehydes into methylketones by means of diazomethane; but it stands in close analogy to the formation of ethyl @-methyl-and a ,@dme$hylcinnamatesfrom ethyl cinnamate and a-methylcinnamate, respectivelyI1, on thermal decomposition of the primarily formed pyrazoline derivatives, and to the formation, from anaphthoquinone and diphenyldiazomethane, of 2benzohydryl-a-naphthoquinone12. While these relationships seem perfectly clear, no analogue so far has been reported for the Fieser reaction proper, the conversion by diazomethane of 2,6-dimethylnaphthoquinoneinto the "bimolecular" product formulated as (XI, X=CHs). (One would aflsume, that its formation is due to a second stabilisation reaction of the radical remaining from the decomposition of the primary addition product.) In fact, we have observed a second case: in the reaction of 2-methylnaphthoquinone with diazomethane, besides the normal addition product, m.p. 114", and 2,310
FIESERAND Dv", J . Am. Chem. Soe., 69, 1016, 1024 (1937).
v. AUWERSAND Ber., 68, 1198 (1933). 11
11
KOENIQ,
Ann. 496, 252 (1932); v. AUWERRAND UNQEYACH,
FIESERAND PETERS,J . Am. Chem. SOC.,63, 4080 (1931).
129
SYNTHESES OF SUBSTITUTED a-NAPHTHOQUINONES
dimethylnaphthoquinone (see above), a “bimolecular” nitrogen-free substance, map. 242O, was obtained, undoubtedly in principle analogous to Fieser’s compound. A minor difference is, that our substance is a diquinone, while Fieser’s, as stated above, contains a hydroquinoid system. Theoretically, it is possible, that the bridge combining the two quinone molecules is built up not by one, but by two carbon atoms, in analogy with the reaction of aromatic nitroso compounds, yielding dinitrones, e.g., CsH6.N(: O)=CH-CH=N(: 0)eCsH5, with dia~omethane’~.Therefore we think it interesting that we can produce an-however indirect-argument in favour of Fieser’s formula. Theoretically, according to the above, the two structures XI1 and XI11 would have to be taken into account, which would not easily be discriminated from (XI, X=H) by purely analytical methods. We were able to obtain the substances XI1 and XIII, which proved different from the above-mentioned diazomethane product,
/\L C H 3 CH3&
I/ I/ I
I /I I x / Y0 A
CH2P
0
X
XI
0
0
XI1
OH
0
XI11
in the following, somewhat surprising way. When 2,3-dimethylnaphthoquinone is treated with benzohydrylsodium, and the product is subsequently exposed to air in the presence of alkali, two products are formedthe differences in formation conditions not being absolutely defined: a diquinone C24H1804, m.p. 261’ or a diquinone, CzrH~aOil,m.p. 228”, to which we ascribe formulas XI1 and XI11 respectively. Benzohydrylsodium, apparently, does not actually take part in the reaction; it is 13 v. PECHMANN, Ber., 30, 2461.2875 (1897); v. PECHMANN AND SCHMITZ, ibid., 31, 293 (1898); v. PECHMANN AND SEEL,ibid., 31, 296 (1898); v. PECRMANN AND NOLD, ibid., 31,557 (1898); BAMBEROER, ibid., 33,945 (1900).
130
ERNST BERQMANN AND FELIX BERGMANN
suggested that it merely enolizes 2,3-dimethylnaphthoquinonel4. So XIV is formed, which adds one molecule of the non-enolized quinone according t o the following scheme:
0
0
OH
0
XIV Subsequently, dehydrogenation takes place to form XI1 or XIII. The acting methyl in the above reaction is activated by the carbonyl group via the conjugated double bond15. The occurrence in XI11 of a double bond is indicated by the observation that alcoholic ferric chloride introduces an additional oxygen atom, forming a substance C24Hle06, m.p. 184'. We did not try to decide whether the entering oxygen atom forms an oxide ring (-CH-CH-) or a keto-group (-CO-CHz-). The enolization
'd
of 2,3-dimethylnaphthoquinone (-tXIV) is in complete analogy to the interconversion of 2-hydroxy-a- and 4-hydroxy-~-naphthoquinones'6. In this connection, it seems worth reporting that the substance (XIII) is obtained also by exposing 2,3-dimethylnaphthoquinoneto air in presence of methyl alcoholic potash solution. This reaction and the above one recall the formation of the dye anthraflavone from 2-methylanthraquinEXPERIMENTAL
d,6,7-Trimethyl-6,8,9,lO-tetrahydro-a-naphthaquinane (I).-Toluquinone (5 9.) and 2,3-dimethylbutadiene (7.5 9.) are heated in a sealed tube a t 110' for ohe hour. The excess dimethylbutadiene is evaporated; the residue crystallizes; from methanol or isopropyl alcohol, needles, m.p. 93-94'. Concentrate sulfuric acid gives a red color reaction. The same product is obtained in boiling benzene solution (4 hours), but at the same time a considerable amount of toluquinhydrone is formed. For references on the enoliaing action of organo-alkali compounds see BERGJ . Chem.Sac.,1936, 412. l6 See FVSON, Chem. Rev.,16, 1 (1935); FVSONAND CO-WORKERS, J. Am. Chem. SOC., 68, 1979, 2450 (1936). Compare, also for references, KUHNAND GRVNDMANN, Ber.,70,1318 (1937). 16 See MEYER-JACOBSOHN, Berlin and Leipzig, 1903, Vol. 11, Part 2, pp. 390-398. IT HOVBEN,"Das Anthracen und die Anthrachinone," Leipzig, 1928, p. 269. Compare BERGMANN AND BLUM-BERQMANN, J . Am. Chem.Sac.,69, 1439 (1937). 14
MANN,
SYNTHESES O F SUBSTITUTED a-NAPHTHOQUINONES
131
Anal. Calc'd for C I ~ H ~ 0 0C, 2 : 76.47; H, 7.84. Found: C, 76.44; H, 7.89. 2,6,7-Trimethyl-5,8-dihydro-l, 4-dihydroxynaphthalene (ZZ).-(a) When to a solution of I (0.1 g.) in glacial acetic acid 1 drop of hydrobromic acid is added, the mass solidifies quickly. The product is collected and precipitated from its dioxane solution by light petroleum (b.p. 80-100"). Needles, m.p. 224". Anal. Calc'd for C13H1602: C, 76.47; H, 7.84. Found: C, 76.43; H, 8.20. ( b ) Toluquinone (8 g.) and 2,3-dimethylbutadiene (12 g.) are heated as above, but at 150-170". The crystalline mass is purified as sub (a); m.p. and mixture m.p. 224"; yield, 12 g. From the mother-liquors, occasionally, a yellow substance separates. It forms, after recrystallisation from isopropyl alcohol and light petroleum (b.p. 80-100°) yellow needles, m.p. 110" which give the same dark-red color reaction with Concentrated sulfuric acid as I or 11, and were identified as 2,6,7trimethylnaphthoquinone (111, see below). 2,6,7-Trimethyl-5,8-dihydro-a-naphthoquinone (ZV).-One gram of I1 is suspended in alcohol and heated with an alcoholic solution of ferric chloride (3 g.) for 5 minutes. On addition of water, yellow crystals are obtained, which are recrystallized from benzine (b.p. 8O-llO0). Long, silky needles, m.p. 129", which still give the dark-red color reaction with concentrated sulfuric acid and suffer slight discoloration on heating or continued exposure to air. Anal. Calc'd for CISHI~OZ: C, 77.23; H, 6.93. Found: C, 77.28; H, 7.20. 8,6,~-Trimethyl-a-naphthoquinone (ZZZ).-(a) The addition product (I) (1 g.) is heated with selenium (1 g.) a t 200-210°, until the evolution of hydrogen selenide ceases. The residue is extracted with ethyl acetate and chloroform. From this solution crystals remain which are triturated with methyl alcohol and recrystallized from light petroleum (b.p. 8O-l0O0). Yellow needles, m.p. 110"; yield 0.1 g. Anal. Calc'd for ClsH1202: C, 78.0; H, 6.0. Found: C, 78.2, 77.4; H, 6.0, 6.1. ( b ) One gram of IV was treated with selenium (0.3 g.) at 280" as sub ( a ) . The product was purified by high vacuum (0.03 mm.) distillation and subsequent recrystallisation from light petroleum. 2-Phenyl-6,7-dimethyl-5,8,9,lO-tetrahydronaphthoquinone ( V ).-Phenylquinon el* (4g.) and 2,3-dimethylbutadine (10 g.) were heated at 100" for one hour in a sealed tube. The product crystallises spontaneously. From light-petroleum, yellowish needles, m.p. 113-114'; yield, 4.5 g. ; dark-red color-reaction with concentrated sulfuric acid. Anal. Calc'd for ClsHlsOt: C, 81.2; H, 6.8. Found: C, 81.19; H, 7.42. 8-Phenyl-6, Y-dimethyl-5,8-dihydro-l, 4-dihydroxynaphthalene (as ZZ).-One hundred milligrams of V is isomerized in glacial acetic acid solution by addition of a few drops of hydrobromic acid. The mixture congeals spontaneously; the product is collected and recrystallized from light petroleum (b.p. 80-100"). The crystals, m.p. 137O, oxidize spontaneously in the air and therefore undergo discoloration quickly. Analyses were very unsatisfactory. Anal. Calc'd for C18H1802:C, 81.2; H, 7.0. Found: C, 79.3; H, 7.4. l8
Preparation according to KVALNES, J. Am. Chem. Soc., 66, 2478 (1934).
132
ERNST BERGMA"
AND FELIX BERGMANN
t-Phenyl-6,7-dimethyl-6,8-dihydro-a-naphthoquinone(as ZZI) .-The foregoing substance is dissolved in alcohol, and ferric chloride solution added. The solution turns first black-green, then brown, and the product separates spontaneously. From isopropyl alcohol orange-red needles, m.p. 119". Bright colors have been found to be characteristic for a-naphthoquinone derivatives with three parallel nuclear double bonds. Anal. Calc'd for ClaHleOn: C, 81.7; H, 6.7. Found: C, 81.3; H, 6.4. 8-Phenyl-6,7-dimethyl-l ,d-dihydroxynaphtha1en.e.-The addition product (V, 2 9.) reacted with selenium (1.5 9.) at 280-300". The greyish reaction product was recrystalliied from ligroin. Stars of prisms, m.p. 197-198"; yield, 1 g. concentrated sulfuric acid gives a violet color reaction. Anal. Calc'd for CISHleOl: C, 81.8; H, 6.1. Found: C, 81.4, 81.7; €3, 6.3, 6.4. 8-Phenyld,7-dimethyZ-a-naphthoquinone.-(a) The foregoing hydroquinone (0.1 g.) was gently heated with alcoholic ferric chloride solution, and the reaction product was precipitated with water. From light petroleum (80-100") yellow clusters of needles, m.p. I n " , which give a violet solution in concentrated sulfuric acid. Anal. Calc'd for ClsH14Os: C, 82.4; H, 5.3. Found: C, 82.2; H, 5.7. (b) 2-Phenyl-6,7-dimethyl-6,8-dihydro-cu-naphthoquinone (as 111), m.p. 119", is dehydrogenated with an equal amount of selenium. (c) Phenylquinone (4 g.) and 2,3-dimethylbutadiene (10 g.) are heated in a sealed tube to 150' for one hour and t o 200' for another hour. The residue remaining after evaporation of the excess dimethyl butadiene was triturated with a mixture of light petroleum (b.p. 40-60") and isopropyl alcohol, and recrystallized from methyl alcohol. The mixture of 2-phenyl-6,7-dimethyl-a-naphthoquinoneand (the prevailing) 2-phenylquinhydrone1O had to be separated mechanically. The melting point of the former, and of its mixtures with known specimens, waa 127". ~-Hydroxy-8-phenyl-6,7-dimethyE-a-naphthoquinone ( V I ).-(a) The addition product (V, 1 g.) was dissolved in 15% methyl alcoholic potash solution, and a stream of air was passed through the liquid. A green precipitate is formed a t first; it dissolves again subsequently, and finally a reddish solution is obtained, which is precipitated with dilute hydrochloric acid. From butyl acetate or ligroin orange-red leaflets, m.p. 158"; yield 6.4 g. The substance dissolves in concentrated sulfuric acid with dark-brown, in methyl alcoholic potash solution with red, color, and gives a darkred coloration with alcoholic ferric chloride solution, a violet one with boric-arctic anhydride. Anal. Calc'd for C I ~ H ~ ~ C, O I77.7; ~ : H, 5.0. Found: C, 78.0, 78.2; H, 5.3, 5.5. The same substance was obtained when the dark-red solution of 2-phenyl-6,7dimethyl-1, 4-dihydroxynaphthalene (m.p. 197-198') waa treated with an air-stream until the color remained reddish. The methyl ether, prepared with diazomethane in violent interaction,t formed greenish-yellow, shiny prisms, m.p. 188' which gave none of the above color reactions. Anal. Calc'd for CIQH1eOs:C, 78.1; H, 5.7. Found: C, 78.5, 78.0; H, 6.3, 6.4. For its formation, compare CRIEQER,Ber., 69,2758 (1936).
t With dimethyl sulfate, no methylation could be forced.
SYNTHESES OF SUBSTITUTED a-NAPHTHOQUINONES
133
Phenylquinone (1.84 g.) and cyclopentadiene (0.66 g.) were heated in benzene solution (10 cc.) for 2 hours on the water bath. After evaporation of the solvent, ligroin was added, a brown syrupy by-product was removed by filtration, and t h e solution was cooled. Long prisms, which were recrystallized from isopropyl alcohol; m.p. 79-80"; yield, 0.45 g. concentrated sulfuric acid gives a dark-red solution. Anal. Calc'd for Cl7H1402: C, 81.6; H, 5.6. Found: C, 81.3; H, 6.0. 8-Bromo-a-naphthoquinone and diazomethane (X).-2-Bromo-cr-naphthoquinone* (2 g . ) were treated with diazomethane (1 g.) in ethereal solution. The violent reaction results in a heavy, bromine-containing precipitate, which after 24 hours' standing (ice box) was collected (m.p. 272-280", dec.), and triturated with concentrated ammonia solution at room temperature. The 3-naphtho [2,3]pyrazole-4,9-dione (X) was filtered and recrystallized from glacial acetic acid; m.p. 345". The substance is undoubtedly identical with that described by Fieser and Petersz'. Its analogy with anthraquinone, as stressed by the American authors, is underlined by the observation that zinc-dust and alkali give a brilliant green vat. Anal. Calc'd for CllHsN202: C, 66.0; H, 3.0. Found: C, 65.7; H, 3.6. Diazomethane and V.-The addition product (V, 0.9 g.) in methyl alcohol reacted quickly upon ethereal diazomethane solution. A small quantity of colorless crystals appeared, which dissolved subsequently. The product, isolated after 24 hours' standing, was a reddish syrup; b.p. 17OoJ0.3 mm. Anal. Calc'd for ClpH~oNaO~: C, 74.0; H, 6.5. Found: C, 74.3; H, 6.8. Diazomethane and I.-The condensation product (I, 1.2 g,), treated with diazomethane as above, gave long white needles, which could be recrystallized from isopropyl alcohol. Stars of stout prisms; m.p. 146" (dec.). Analysis showed, that a true addition-product was formed. Anal. Calc'd for ClrH~sN~O2: C, 68.3; H, 7.3; N, 11.4. Found: C, 68.6, 68.3; H, 7.7, 7.4; N, 11.7. When this product (0.2 g.) was boiled in ligroin for 1 hour, and the solvent was removed, a resinous residue was obtained. This was isomerized in glacial acetic acid solution by means of hydrobromic acid, and the product (m.p. 232') was subsequently oxidised with ferric chloride in alcoholic solution. The S,J,6,r-tetramethyl-6,8-dihydro-a-naphthoquinone( I X ) , so obtained, formed brown-red needles, from isopropyl alcohol; m.p. 155-156". Anal. Calc'd for Cl4H1602: C, 77.8; H, 7.4. Found: C, 77.4, 77.9; H, 7.1, 7.3. Diazomethane and I, 6,7-trimethylnaphthoquinone (111).-Diazomethane reacted on standing a t room temperature for 24 hours with 2,6,7-trimethyl-a-naphthoquinone (0.3 g.) in methyl alcohol solution. The solution was evaporated, and the residue was triturated with a mixture of acetone and light petroleum (b.p. 40-80'). The m.p. (175") of the product fell on recrystallisation from a mixture of butyl acetate and ligroin; i t was constant a t 167-168". Apparently, oxidation had taken place, the final product being I,S,6,7-tetramethyl-a-naphthoquinone. Concentrate sulfuric acid gives a red-violet color-reaction. Anal. Calc'd for Cl4HlrO2: C, 78.5; H, 6.6; mol. wt., 234. Found: C, 78.8, 78.4; H, 7.0, 6.7; mol. wt./e(camphor), 234. 20
ZINCKEAND SCHMIDT, Ber., 27, 2753 (1894).
134
ERNST BERGMA" AND FELIX BERGMA"
It may seem surprising, t h a t a hydroquinone should have been formed in the presence of excess diazomethane. Obviously, the methylation is sterically hindered. Similar observations have been made by Fieser and co-workers,11z1 and recently by Hill, Short, and Str0mberg.n Diazomethane and 2-methylnaphthoquinone ( X I , X = H).-The quinone2* (3 g.) was kept with ethereal diazomethane solution (10 moles) a t 0" for 24 hours. Then the solution was evaporated, the residue, which solidified almost completely, was recrystallized from methyl alcohol, and the mixture of white and yellow crystals so obtained was separated mechanically. The white needles, from benzene-light petroleum (b.p. 80-100"), m.p. 114", were the true addition product. Anal. Calc'd for C12HloNaOl: C, 67.3;H, 4.7;N, 13.1. Found: C, 67.5;H I 4.8; N, 13.1. The yellow prismatic needles were recrystallized from butanol and had m.p. 242" (XI, X = H). Ferric chloride in alcoholic solution caused no change. Anal. Calc'd for C2sHls04:C, 77.5; H, 4.5. Found: C, 77.4;H, 4.7. The original mother-liquor of both these substances was distilled under high vacuum, and the distillate was treated with methyl alcohol. Yellow needles (m.p. 122") separated, and the melting point was not depressed on admixture of 2,3dimethylnaphthoquinone. We cannot confirm the statement of Marbeth and Winzorz4that 2-methylnaphthoquinone is resistant toward diazomethane. Diazomethane and 2,6-dimethylnaphthoquinone(+XI, X = CHs) .-The quinonez6 (7.5 9.) was kept a t 0" with diazomethane (3 9.) for 24 hours, and, after addition of another gram of diazomethane, one day more. The precipitate was collected and recrystallized several times from boiling xylene. Yellow, lancet-shaped crystals; m.p. 293" (slight dec.). Concentrate sulfuric acid gives a brilliant-red, methyl alcoholic potash solution a greenish-blue, solution. The substance has been assumed our analyses accord very well with the forby Fieser' to be a diquinone, CZ~HZOO,; mula C Z ~ H I ~ O ~ . Anal. Calc'd for C26H2204: C, 77.6; H, 5.7; active HI 0.52. Found: C, 78.4,78.4;H , 5.8, 5.8;active H , 0.38. Dehydrogenation with alcoholic ferric chloride solution, yields dark-yellow crystals, from a mixture of benzene-light petroleum; m.p. 249". Anal. Calc'd for C ~ ~ H Z ~C, O ,77.2; : H, 5.2. Found: C, 77.8, 77.6;H, 5.7, 4.8. The mother liquor, from which the described substance had separated, was distilled several times under high vacuum. The oil, distilling finally a t 140°/1 mm., crystallized from alcohol on standing; m.p. 100". The analysis of the crystals pointed definitely to the formula of a 2,3,6-trimethylnaphthoquinone. Anal. Calc'd for C1sH1202: C, 78.0; H, 6.0. Found: C, 77.5;H, 5.7. In some cases, an additional reaction product, from butyl acetate, m.p. 228.5", was secured; due to the scarcity of material available, its structure was not investigated. dl6-Dimethyl-l,4-naphthalenediol and i t s dimethyl ether: In connection with the FIESER AND PETERS, J . Am. Chem. SOC.,63,4080 (1931). HILL, SHORT,AND STROMBERG, J . Chem. SOC.,1937, 937. 25 MADINAVEITIA AND DE BURUAGA, Chem. Zentr., 1930, I, 684. 24 MARBETH AND WINZOR,J . Chem. Soc., 1936, 334. 2) WEISSGERBER AND KRUBER,Ber., 62,356 (1919). 21 Z2
SYNTHESES OF SUBSTITUTED a-NAPHTHOQUINONE8
135
reported experiments, 2,6-dimethylnaphthoquinonehas been reduced. The quinone (15 g.) and zinc dust (30 g.) were suspended in boiling alcohol (100 cc.), and a few cubic centimeters of glacial acetic acid was added. After fifteen minutes' boiling, the solution was filtered while still hot, and the product was precipitated with dilute sulfuric acid. The white crystals, after recrystallisation from benzene, had m.p. 187-188". Anal. Calc'd for C12H1202: C, 76.6; H, 6.4. Found: C, 76.5; H, 6.4. Dimethyl ether.-The hydroquinone (10 g.) and methyl p-toluenesulphonate (15 g.) were heated with methyl alcohol (50 cc.) and 10% potash solution (40 cc., after 1hour's boiling another 50 cc.) was added. After two more hours, the reaction mass was cooled t o O"C, the crystals collected, dissolved in ether, treated with dilute pota.sh solution and finally purified by distillation: b.p. 129"/0.5 mm. The distillate solidified immediately and was recrystallized from light petroleum (b.p. 80-100"). Long, colorless needles, m.p. 75-76". Anal. Calc'd for Cl4Hl602: C, 77.8; H, 7.4. Found: C, 77.9; H, 7.3. Experiments un'th 2,s-dimethy1naphthoquinone.-(a) 2,3-dimethylnaphthoquinoneP6 (2 g.) in methyl alcohol was kept for 10 minutes with a few drops of 15% methyl alcoholic potash solution. The brown-red liquid was acidified with alcoholic hydrochloric acid, filtered, and evaporated. From butyl acetate, ligroin, or xylene, yellow needles, m.p. 227-228" (XIII), which dissolve in concentrated sulfuric acid with dark-violet coloration. Anal. Calc'd for CzaHlgO~: C, 77.8; H, 4.2; active H, 0.54; mol. wt., 370. Found: C, 78.3; H, 4.7; active H, 0.54; mol. wt. (camphor), 319. Oxidation.-The foregoing substance (200 mg.) was suspended in alcohol and for some minutes boiled with an alcoholic solution (5 cc.) of ferric chloride (1 g.). The substance passed into solution, and the reaction product had to be precipitated with water. From xylene, stout prisms, from ligroin plates, m.p. 184". Analysis points t o the formula C24H1606. Anal. Calc'd for C ~ , H I ~ O C, S : 75.0; H, 4.2. Found: C, 74.7; H, 5.6. (a) Benzohydrylsodium, prepared from benzohydryl methyl ether" (4.2 9.) was added t o 2,3-dimethylnaphthoquinone (1.9 g.). The green mass, after 24 hours' standing, was decomposed with alcohol, and poured out into water. The ethereal layer contained tetraphenylethane, which was identified by melting point and mixture melting point (207"), and a yellow substance, which had to be separated mechanically and then was recrystallized several times from light petroleum (80100"). Eventually, i t formed needles, which melted a t 167", and according t o the analysis represented 2-(a, P-diphenylethyl)-3-methylnaphthoquinone.
n
Preparation: SMITHAND WEBSTER,J . Am. Chem. Soc., 69, 664 (1937). ZIEGIERAND THIELMANN, Ber., 66,1740 (1923); SCHLENK AND BERGMANN, Ann., 464, 18 (1928). 26
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ERNST BERGMA" AND FELIX BERGMANN
Anal. Calc'd for C Z ~ I ~ O C, O Z85.2; : H, 5.7. Found: C, 84.8; H, 5.7. Its formation is explained by 1,4 addition of benaohydrylsodium t o the enolic form (XIV) of 2,3-dimethylnaphthoquinone,and subsequent dehydrogenation by means of air or some constituent of the reaction mixture. Through the red alkaline aqueous solution a stream of air was passed, whereby a lighter red solution was obtained. A yellow crystalline mass precipitated, partly spontaneously, partly on acidification. From butyl acetate beautiful needles, m.p. 261-262", which gave a gold-red solution in concentrate sulfuric acid (XII). Anal. Calc'd for C Z ~ H I ~C, O ~77.8; : H, 5.0. Found: C, 77.7, 77.8; H, 5.5, 5.3. In some runs, without discernible reason, the previously-mentioned isomer, m.p. 228", was obtained instead.
